There are two types of recirculation systems: demand-controlled and gravity-fed. A demand-controlled system operates on an electric pump that activates by flipping a switch. A gravity-fed system uses thermosiphoning. This is where cold water falls to the bottom due to its density and hot water rises up.
A recirculation system allows for hot water to reach taps instantly. It provides both comfort and convenience while also saving fresh water that would otherwise be wasted from homeowners waiting for their hot water to reach their shower heads or faucets. A recirculation system can save thousands of gallons of water every year.